Stoker apparatus



Sept. 26, 1944. D. J; M siAAT 2 2,358,993

STOKER APPARATUS Original Filed NOV. 7, 1939 FIG. 1.

WITNESSES: INVENTOR W i Dounw J. Mossunm 6. .H. BY Li?) C1,, f5, M

ATTORN EY Patented Sept. 26, 1944 STO'KER APPARATUS Donald J. Mosshart, Ardmore, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Original application November 7, 1939, Serial N 0. 303,197. Divided and this application August 14, 1943, Serial No. 498,721

3 Claims.

water wall which extends upwardly and over the overfeed section in suitable, spaced relation with respect to the latter so as to improve combustion and to avoid stratification of gases passing upwardly in the furnace chamber from the fuel bed.

With stokers of the underfeed type, the overall effective length may be increased b the provision of an overfeed section of suitable length; and, in order that the fuel bed may be effectively handled by the overfeed section, it is desirable that the latter shall incorporate movable grate elements which agitate the fuel bed to break up fused masses and to secure more thorough permeation of the bed by air. There is a tendency for the gaseous media issuing from the overfeed section to pass upwardly in a stratified condition, that is, adjacent portions of the upwardly moving gases may have a wide variation in the ratio of combustible to air, some portions being overrich in combustible and some having excess air; and, in extreme cases, stratification may result in such incomplete combustion that smoke in substantial quantities is discharged. The irregularity in gaseous media issuing from the overfeed section will be apparent when one considers what occur when a fused mass is fractured due to agitation. Immediately, there ensues vigorous emission of volatile matter and the local air supply may be inadequate to promote complete combustion immediately above the fuel bed. On the other hand, the reverse situation may occur with respect to an adjacent region on the overfeed section, this being particularly true as the rear end of the overfeed section is approached. Accordingly, therefore, I provide a water wall forming the back wall of the furnace chamber and which extends upwardly at the rear of the discharge end of the overfeed section and which then extends upwardly and forwardly in suitable spaced relation with respect to the overfeed section so as to provide a wall substantially covering or overlapping the overfeed section, such wall promoting turbulence and more thorough mixture of gases issuing from the overfeed section with the result that more complete combustion is thereby secured. Aside from the wall promoting turbulence to secure more complete combustion of the gaseous media, it also serves to deflect particles of fuel or ash from the gas stream and backwardly onto the fuel bed to reduce the quantity of such particles that may be carried along with the gases through the gas passages of a boiler installation, whereby the amount of such particles deposited on the battles, the tubes, and possibly carried out through the stack, may be substantially reduced. A further object of my invention is, therefore, to provide combustion apparatus havin these advantageous features of construction and operation.

A further object of my invention is to provide an inclined multiple retort stoker having an overfeed section including movable grate elements together with a rear water wall which overlaps the overfeed section and in suitable spaced relation with respect to the latter to promote turbulence of gaseous media issuing from the fuel bed on the overfeed section together with means for admitting secondary air through the Water wall at the upper end of the portion which overlaps the overfeed section.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawing, forming a part of this application, in which:

The figure is a vertical sectional view showing my improved water wall construction in relation to the stoker and to the furnace chamber and boiler.

Referring now to the drawing more in detail, an inclined stoker, at l0, forms the bottom wall of the furnace chamber II, the stoker bein of a well-known type and including a multiple retort underfeed section I2 followed by an overfeed section [3, the overfeed section comprising a mul tiplicity of moving grate elements indicated generally at M and which serve to agitate the fuel bed passing over the overfeed section and to promote the travel thereof in the direction of fuel feed.

A water wall [5 including upwardly-extending parallel tubes It extends upwardly at the rear of the discharge end of the overfeed section and then forwardly and upwardly so as to overlap the latter, thereby providing a turbulence space or chamber between the fuel bed on the overfeed section and such overlapping portion of the water wall to promote more thorough mixture or turbulence of gaseous media issuing from the fuel bed, the turbulence chamber or space so provided insuring a more thorough mixture of the gases and better combustion thereof with minimized stratification and smoking on that account.

In the figure, the invention is shown as applied to a stoker having an ash pit I! from which ash and refuse are discharged by means of the clinker grinder 18, the accumulations of ash and refuse in the pit ll above the clinker grinder serving in the usual way to seal the furnace chamber H against the ingress of air. In this embodiment, the water wall includes: the lower'header 2t from which the first vertical section, at 2|, extends upwardly to a rear wall portion common both to the ash pit I! and to the furnace chamber H; a second section, at 22, continuous with the first section, at 2|, and which extends upwardly and forwardly toward the front wall 23 of the furnace chamber so as to cover or overlap the vertical projection of the ash pit H; a third section, at 24, continuous with the second section and which extends upwardly and forwardly toward the front wall 23 but with a greater degree of horizontal component of direction than the second section; and a fourth section, at 25, continuous with the third section and which extends upwardly, the junction of the sections '24 and 25 providing an angular or reentrant portion 26, which, with the furnace'front wall 23, forms an orifice area in the furnace chamber above the stoker.

An air chamber 21 is arranged transversely and rearwardly of the junction portion 26 so that spaces between tubes at the junction portion may provide openings for issuance of air from the chamber 21 into th furnace chamber ll. Air is supplied to the chamber 2'! by a conduit 28, in turn, supplied by any suitable means. As shown in the figure, air is supplied to the conduit 28 from the conduit 29 connecting the air preheater 3D with the plenum chamber 3| of the stoker, the conduits having dampers 32 and 33 to secure appropriate division of the air.

Aside from the feature of having the water wall overlap the overfeed section to promote turbulence of gases and more thorough combustion, the admission of secondary air at the junction portion 26 further aids in promoting turbulence and more effective and complete combustion, particularly as such air is admitted generally in a horizontal direction and transversely of the throat or orifice of the gaseous flow passage of the furnace and boiler chamber. Furthermore, the overlapping water wall feature and the secondary air admission assists in the settlement of particles, carried from the overfeed section by the gas stream, back onto the underfeed section and promotes, for a given furnace chamber volume, a relatively long path of gas travel, the length. being increased because of the sinuous nature given thereto by the overlapping wall feature and by the energy of the entering secondary air. Furthermore, by having the secondary air admitted through the junction portion 26, it is assured that, not only shall the effect thereof be uniform'throughout the width of the Stoker, but it is admitted to a region having a minimum distance with respect to the horizontal dimensions of the furnace chamber, with the result that most effective penetration of the gas stream by the transverse stream of entering secondary air is secured.

In the arrangement described, not only does the section of the water wall overlapping the overfeed section promote better turbulence in a mixture of the gases issuing from the overfeed section, but the directive effect of such wall causes the stream of such gases to be projected forwardly toward the front wall of the furnace chamber with the result that such gases are caused to mix thoroughly with gases issuing from the underfeed section, whereby more thorough mixture of all of the gases and combustion may be secured. Also, as already pointed out, this forward directive effect promotes deposition of ash and particles back onto the underfeed section and gives a longer path of gas travel and, therefore, an increased time element for a given gas velocity to promote more complete combustion.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and it is desired, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

This application is a division of mycopending application, Serial No. 303,197, filed November 7, 1939 now Patent No. 2,347,574 granted April 25, 1944.

What is claimed is:

1. The combination with a stoker forming th bottom of a furnace chamber and including a multiple retort underfeed section followed, in the direction of fuel feed, by an overfeed section including movable grate elements for agitating the fuel bed passing thereover: of a water wall forming the back wall of the furnace chamber and including upwardly-extending parallel tubes; said water wall including one section extending upwardly at the rear of the discharge end of the overfeed section, another section continuous with said one section and extending upwardly and forwardly toward the front wall of the furnace chamber and in spaced parallel relation with respect to the overfeed section so as to cover substantially the latter, and yet another section which extends upwardly; the directions of extent of the two last-mentioned sections providing an angular or re-entrant junction portion; means providing a chamber supplied with air under pressure extending transversely and rearwardly of the re-entrant portion with the spaces between tubes at the re-entrant portion providing openings for air to issue from the chamber.

2. The combination with an inclined stoker forming the bottom of a furnace chamber and including a-multiple retort underfeed section followed, in the direction of fuel feed, by an overfeed section including movable grate elements for agitating the fuel bed: of a water wall forming the back Wall of the ash pit and of the furnace chamber and including upwardly-extending parallel water tubes; said water wall including a vertical section extending upwardly at the rear of the discharge end of the overfeed section, another section continuous with the vertical section and extending upwardly and forwardly in spaced relation to the overfeed section of the stoker toward the furnace chamber front wall so as to overlap substantially said overfeed section, and yet another section continuous with the upwardly and forwardly extending section and which extends upwardly, the directions of extent of the two last-mentioned sections providing an angular or' re-entrant junction portion which defines, with the front wall, an orifice in the gas flow passage of the chamber; and means providing a chamber supplied with air under pressure and which extends transversely and rearwardly of the re-entrant portion with the spaces between tubes at the re-entrant port1on forming openings for air to issue from the chamber horizontally or transversely of the orifice.

3. The combination with an inclined stoker forming the bottom of a furnace chamber and means providing a vertically-disposed ash pit for ash and refuse discharged from the stoker, said stoker comprising a multiple retort underfeed section followed, in the direction of fuel feed, by an overfeed section including movable grate elements for agitating the fuel bed: of a water wall forming the back wall of the ash pit and of the furnace chamber and including upwardly-extending parallel tubes; said water wall including a first vertical section forming a wall portion which is common to the ash pit and to the furnace chamber, a second section continuous with the first section and extending upwardly and forwardly in the direction of the furnace chamher front Wall so as to overlap substantially the ash pit, a third section continuous with the secend section and extending upwardly and forwardly toward the furnace chamber front wall but with a larger horizontal component of direction than the second section and in spaced parallel relation to the overfeed section so as to overlap the latter, and a fourth section continuous with the third section and which extends upwardly and rearwardly, the directions of extent of the third and fourth sections providing a re-entrant junction portion; and means providing a chamber supplied with air under pressure and extending transversely and rearwardly of the re-entrant portion with the spaces between tubes at the re-entrant portion providing openings for air to issue from the chamber into the furnace chamber.

DONALD J. MOSSHART. 

